1. Field of the Invention
The present invention relates to a lubricant atomizer which is capable of atomizing a given lubricant into fog, and directing the lubricant fog to a given object such as bearings, toothed wheels, sliding parts and such like for lubrication. More particularly, the present invention relates to a circulating type of lubricant atomizer which is capable of producing a constant quantity of atomized lubricant per unit time continuously for an elongated period, and a method of producing a constant quantity of atomized lubricant per unit time continuously for an elongated period.
2. Related Arts
Referring to FIG. 3, a conventional lubricant atomizer uses a manifold 21 to convey atomized lubricant to its branch pipes 22. As shown in the drawing, each branch pipe 22 is connected to a ball bearing, a roll bearing, toothed wheels meshed together, a sprocket wheel and a sliding beam. It is necessary that atomized lubricant whose particles are below 2 or less micron meters in diameter be selected and transferred from the atomizer 24 to each feeding point partly because otherwise, atomized lubricant of larger particles is apt to be condensed on the way to the feeding point in the manifold, and partly because atomized lubricant of larger particles cannot be distributed to all branch nozzles as much as required by their sizes. This sort of lubricant atomizer is called xe2x80x9cselective type of atomized lubricant distributorxe2x80x9d.
Referring to FIG. 4, the atomizer 24 works as follows: compressed air is directed to the entrance 25. When passing through the Venturi mechanism 5 (atomizing unit), the compressed air draws the air from the inner space 6a of the sight dome 6 while sucking and raising the lubricant from the lubricant bath 10 of the oil vessel 9 to the inside space 6a of the sight dome 6. Then, the lubricant is allowed to fall down from the inner space 6a of the sight dome 6 to the center of the Venturi mechanism 5 in the form of droplets. Then, the lubricant droplets are carried by the compressed air to be ejected downward. The so ejected atomized lubricant strike against the interference plate 7a, allowing lubricant particles of relatively large size to stick on the interference plate 7a. Finally, the lubricant falls down from the interference plate 7a in the oil vessel 9 in the form of droplets.
After passing through the interference plate 7, the atomized lubricant spreads in the atomized lubricant separating space 8a in the upper part of the oil vessel 9, where lubricant particles of relatively large size are allowed to fall downward while very small lubricant particles floating there are carried by the flow of compressed air to be ejected from the outlet 14a in the form of fog.
Such a selective type of lubricant atomizer, however, has following defects:
1) The fogging rate (the ratio of the quantity of lubricant atomized and ejected from the atomizer to the quantity of lubricant drawn by the siphon tube 27 to be supplied to the Venturi mechanism 5) will vary with different kinds of lubricant even if the air pressure, the air flow rate, the surrounding temperature, the lubricant temperature and other operating conditions remain unchanged (see FIG. 7); this uncertainty may be attributable to different additives such as oiliness improver, oxidative stabilizer, high-pressure additive or anti-foam agent, among which there are some high polymers causing an adverse effect on the atomizing of lubricant; and to the possibility of arbitrarily changing additives in the lubricants which are sold under same trade names, without informing purchasers of such change. The fogging rate of new lubricants, therefore, needs to be determined prior to use, and the fogging rate of familiar lubricants needs to be checked from time to time.
2) The fogging rate will be affected by the time-variable operating conditions such as the lubricant feeding pressure, the quantity of air flowing from the air bypass into the lubricant conveying line, the daily or seasonal change of surrounding temperature and other factors which are liable to change after the atomizer has been working a certain length of time while using one and same lubricant.
3) The fogging rate will be affected by the deterioration of mechanical parts of the atomizer after elongated use as for instance follows: the Venturi mechanism is apt to be contaminated with dust or oil vapor contained in compressed air; and the lubricant nozzles are apt to be clogged.
4) These defects lead to the difficulty in controlling the absolute quantity of lubricant per unit time, which is contained in the fog ejected from the atomizer. The constant feeding pump positioned in the lubricant feeding line can supply a constant quantity of lubricant to the sight dome of the atomizer, but the varying of the fogging rate will cause the quantity of lubricant from the constant feeding pump to vary accordingly. The absolute quantity of lubricant per unit time ejected from the atomizer can be measured in terms of the descending of the surface level of the lubricant bath. As a matter of fact, however, the descending rate per unit time is so small that a significant measurement requires an elongated time involved therefor.
In the hope of solving such problems, Japanese Patent 10-19192(A) and Utility Model 2580280(B) proposed improved atomizers which are capable of atomizing a controlled quantity of lubricant per unit time.
As shown in FIGS. 5a, 5b and 5c, the former lubricant atomizer uses a lubricant fog sensor 28, which is positioned in the lubricant feeding line 14 to detect changes, if any in the working factors (the lubricant feeding pressure, the quantity of air added to the lubricant feeding line from the air bypass, or the surrounding temperature) and in the fogging rate and the fog density in the lubricant feeding line 14, thereby permitting the controlling of the quantity of lubricant to be supplied to the Venturi mechanism 5 for keeping the fog density unchanged.
As shown in FIG. 6, the latter lubricant atomizer comprises a top sight dome 6 for watching the falling of lubricant droplets, a Venturi mechanism 5 having an air feeding line 25 connected thereto, and a pressurized vessel 8. The Venturi mechanism 5 has an interference 7 formed on its ejecting side, thereby allowing the fog to strike against the interference 7. Impingement at the interference 7 grows relatively large fog particles to large droplets, which fall downward. Solid contaminant in the oil functions as a core of fog particle at the atomizing process and check oil to form the fine fog. Relatively large fog particles containing solid contaminants also fall down on the bottom of the pressurized vessel 8. The lubricant thus collected on the bottom of the pressurized vessel 8 contains a significant amount of dust, and therefore, such contaminated lubricant oil is difficult to be atomized. The lubricant oil remaining on the bottom of the pressurized vessel 8 is filtered with passing through the filter 11, and the filtrate is drawn by the sucking pump 26 to return to the oil vessel 9. Thus, the fogging rate is stabilized.
As for the lubricant atomizer disclosed in Japanese Patent 10-19192(A), the lubricant fog sensor 28 and the arithmetic control (FIG. 5b) are inhibitably expensive, and therefore its use is limited to extra need.
As for the lubricant atomizer disclosed in Japanese Utility Model 2580280(B), the lubricant is fed at a constant rate by using a constant feeding pump 12. Contaminant is removed from compressed air and lubricant oil, thereby providing very small particles of lubricant in the fog. Thus, the fogging rate is improved, and at the same time, the fogging rate is stabilized. The proposed lubricant atomizer, however, cannot solve all of the problems 1, 2, 3 and 4 described above.
In view of the above, one object of the present invention is to provide a method of atomizing lubricant at a constant rate in a lubricant atomizer irrespective of the kinds of lubricant and the working conditions. Another object of the present invention is to provide a circulating type of constant-rated lubricant atomizer which is less expensive, and is capable of atomizing lubricant at a constant rate irrespective of the kinds of lubricant and the working conditions.
To attain these objects a method of atomizing lubricant at a constant rate in a lubricant atomizer comprising a compressed air valve having two or more ports and two branches on its downstream side, a sight dome, a pressurized oil vessel integrally connected to the sight dome with an intervening Venturi mechanism fixed therebetween, and a constant lubricant supplying pump, one of the two branches of the compressed air valve being connected to the Venturi mechanism, and the other branch being connected to the constant lubricant supplying pump, the method comprising the steps of; supplying filtrated, pressure-controlled compressed air to the Venturi mechanism via one of the two branches of the compressed air valve and to the constant lubricant supplying pump via the other branch of the compressed air valve respectively, thus drawing the air from the sight dome while the compressed air is flowing in the Venturi mechanism; supplying lubricant from the constant lubricant supplying pump to the sight dome via an associated constant lubricant supplying conduit, allowing the lubricant to fall in the center of the Venturi mechanism in the form of droplets; mixing compressed air with lubricant droplets to form the fog of atomized lubricant in the pressurized oil vessel; allowing atomized lubricant to condense into lubricant droplets in the atomized-and-condensed lubricant coexistent space of the pressurized oil vessel; and allowing the lubricant droplets to fall down on the bottom of the pressurized oil vessel while ejecting the fog of atomized lubricant from the pressurized oil vessel, is improved according to the present invention in that it further comprises the step of using the negative pressure provided by the Venturi mechanism to draw the lubricant remaining on the bottom of the pressurized oil vessel via an associated lubricant circulating conduit opening at the bottom of the pressurized oil vessel, thereby making lubricant to return to the lubricant fed-back space defined above the Venturi mechanism, thus permitting lubricant to be atomized continuously.
Lubricant may be drawn from the bottom of the oil vessel via an associated filter after putting the plunger pump in operation by actuating an associated three-port electromagnetic valve, via which the compressed air is supplied from the other branch of the compressed air valve to the plunger pump; the Venturi mechanism may comprise a Venturi body and an associated holder; a predetermined quantity of lubricant may be supplied to the sight dome via the constant lubricant supplying conduit; the lubricant fed-back space may be defined above the Venturi body in the Venturi holder, the Venturi holder having at least one through hole to allow lubricant to drop from the sight dome to the lubricant fed-back space; and the lubricant fed back to the lubricant fed-back space may be joined with the lubricant falling down in the lubricant fed-back space.
A circulating type of constant-rated lubricant atomizer according to the present invention comprises: an on-and-off compressed air valve having two or more ports and two branches on its downstream side, a sight dome, a pressurized oil vessel integrally connected to the sight dome with an intervening Venturi mechanism fixed therebetween, a constant lubricant oil supplying pump, one of the two branches of the compressed air valve being connected to the Venturi mechanism, and the other branch being connected to the constant lubricant oil supplying pump, and a lubricant circulating conduit opening at the bottom of the pressurized oil vessel, thereby making lubricant to return to the Venturi mechanism, thus permitting lubricant oil to be atomized continuously.
The Venturi mechanism may comprise a Venturi body and an associated Venturi holder having one or more through holes; a lubricant fed-back space may be defined above the Venturi body in the Venturi holder so that the lubricant fed-back space communicates with the sight dome via the through hole, and the lubricant circulating conduit may be connected to the lubricant fed-back space via a passage formed at a level higher than the Venturi body.
The constant lubricant oil supplying pump may comprise a plunger pump communicating with an oil vessel, and a three-ported electromagnetic valve connected to the on-and-off compressed air valve, thus permitting the plunger pump to work through the on-and-off operation of the electromagnetic valve, thereby drawing a predetermined quantity of lubricant from the oil vessel after being filtered by a lubricant filter provided in the oil vessel so that the sight dome may be supplied with the predetermined quantity of lubricant via the constant lubricant supplying conduit.
The pressurized oil vessel may have a level switch and/or lubricant drain valve equipped therewith.
Other objects and advantages of the present invention will be understood from the following description of one preferred embodiment of the present invention, which is shown in accompanying drawings.